Vacuum tube



Oct. 23, 1928.

E. W. ENG LE VACUUM TUBE Filed April 14, 1926 Patented Oct. 23, 1928.

EDGAR w. snow, of

LAKE FOREST, ILLINOIS, ASSIGNOR TO FANSTEEL PRODUCTS COMPANY, INQ, OF NORTH CHICAGO, ILLINOIS, A CORPORATION OF NEW YORK.

vacuum TUBE.

Application filed April 14,

My invention relates to vacuum tubes such as are used for radio receivers and transmitters and in which a heated filament is employed.

4 It is an object of my invention to provide an improved means for eliminating the last traces of gases found in the tube afterthe process of mechanical exhaustion has been completed.

It is the further object of my invention to provide improved means for eliminating the traces of gases from vacuum tubes continuously while the tube is in use.

Other objects will appear from the following description, reference being had to the accompanying drawings in which:

Figure 1 is a vertical sectional view of a conventional vacuum tube.

Figure 2 is a horizontal section thereof taken on the line 2-2 of Figure 1.

Figure 3 is a bottom plan view of the tube shown in Figure 1.

Figure 4 is a detailed view of a filament showing one embodiment of my invention.

Figure 5 is a view similar to Figure 4 showing a second embodiment of my invention.

When metallic tantalum is heated to a temperature at which it is a dull red color, it has the property of absorbing or occluding large quantities of most gases. My invention employs this property of tantalum to remove the last traces of gases present in vacuum tubes such as used for radio sets.

Figure 1 shows a vertical section of a conventional tube of the type as generally used in radio receivers. It consists of a glass bulb 6, a .glass body 7 and the usual metallic or non-conducting mounting 8. A plate 9 and a grid 10 are suitably supported within the tube and are connected by conductors to the terminal posts 11. A filament 12 is similarly supported within the grid and is likewise connected to terminal posts 11.

Thus far the usual conventional construction of a vacuum tube has been described. My invention contemplates winding a helical coil 13 of tantalum wire around a portion of the filament. This coil will be heated by conduc- 5 tion from the filament whenever the tube is being used. Its size may be such that'it will normally attain a temperature at which it is 1926. Serial No. 101,900.

a dull red color so that it will absorb any slight amounts of gas which may have been left in the tube after it has been sealed. The

coil will, of course, last as long as the filament and the tube will, therefore, be kept free from gas throughout its. entire life, and although the coil is of very small dimensions it is capable of absorbing a considerable quantity of gases and will, under ordinary circumstances, effectively maintain a very nearly perfect vacuum in the tube.

In Figure 5 I have shown a modification of the invention above described in that the coil 14: of tantalum wire actsas a support for the filament. In this construction the coil is preferably made in diameter considerably larger than the diameter of the filament Wire so that the filament may be readily threaded through the coil. The action of the coil in this construction is practically the same as that of the tantalum coil shown in Figure 4. In each of these modifications the coil is heated for the most part by heat conducted from the filament, although it is heated to a very slight extent by the small amount of current which would naturally pass through it.

It will be noted thatthe tantalum is not subjected to any great mechanical strains so that even though it should become brittle through the absorption of great quantities of gases yet this would not impair its efiiciency or the efficiency of, the tube.

While I have shown and described my invention with reference to the specific embodiments, it will be apparent that its prlnciples may be applied in a wide variety of constructions. I contemplate such variation as may be desirable or useful in the particular adaptation of the invention shown or in its adaptation to other similar devices.

I do not restrict myself in any unessential particulars, but what I claim and desire to secure by Letters Patent is:

In a vacuum tube for radio purposes, a filameiit and a support therefor, the end of said support being made of tantalum and being wound about said filament so as to be heated thereby and absorb traces of gases which may be present in the tube. v

'In witness whereof, I hereunto subscribe myname this 5 day of April, 1926. EDGAR W. ENGLE. 

